At the end of the sixteenth century, the English lawyer and natural philosopher Francis Bacon (1561–1626) began to fantasize about the locations for knowledge. The Gesta Grayorum (1594), a court revel performed before Queen Elizabeth I and attributed to Bacon, described an imaginary research facility containing “a most perfect and general library” and “a spacious, wonderful garden” filled with wild and cultivated plants and surrounded by a menagerie, aviary, freshwater lake, and saltwater lake. Spaces for living nature were complemented by a museum of science, art, and technology – “a goodly huge cabinet” housing artifacts (“whatsoever the hand of man by exquisite art or engine has made rare in stuff”), natural oddities (“whatsoever singularity, chance, and the shuffle of things hath produced”), and gems, minerals, and fossils (“whatsoever Nature has wrought in things that want life and may be kept”). The fourth and final component was a space in which to test nature, “a still-house, so furnished with mills, instruments, furnaces, and vessels as may be a palace fit for a philosopher’s stone.” The totality of these facilities, Bacon concluded, would be “a model of the universal nature made private.” This statement suggested a new idea of empiricism that privileged human invention and demonstration over pure observation and celebrated the communal aspects of observing nature over the heroic efforts of the lone observer. Nature had to be reconstructed within a microcosm, creating an artificial world of knowledge in which scholars prodded, dissected, and experimented with nature in order to know it better.

In the midst of his great Historia animalium (History of Animals, 1551–8), the Swiss-German naturalist Conrad Gessner (1516–1565) offered the following reflection on the process of creating knowledge. “Reason and experience are the two pillars of scientific work,” he affirmed. “Reason comes to us from God; experience depends on the will of man. Science is born from the collaboration of the two.” Gessner’s experience gathering materials for a new history of nature in the mid-sixteenth century gave him direct insight into the problems of combining reason and experience. The more material he uncovered, the more difficult it was to organize the natural world into distinctly logical patterns. By placing great emphasis on experience, Gessner had amassed enough material to write four hefty volumes that far surpassed what anyone had known before about animals. But he confessed that experience alone was an undisciplined kind of knowledge. It was reason that allowed him to give some semblance of order to nature and to interpret the similarities and differences he saw among the natural things of the world.

Gessner’s methodological lessons in the midst of his Renaissance zoology remind us that the natural sciences were an important arena in which new definitions of knowledge arose from an increased emphasis on experience. In the early modern period, natural history was an important, controversial, and much discussed kind of knowledge. Natural history was a truly encyclopedic science in which broad sectors of society participated, although not, at this point, as a unified group. Learned scholars delighted in the questions of terminology that allowed them to use their formidable linguistic erudition, developing a more precise vocabulary for the natural world that conformed to their experience of it.

During the second half of the seventeenth century two men in particular occupied a prominent place in the world of natural philosophy. Inhabiting respectively the capital cities of Rome and London, they had much in common. Both were deeply religious men, committed to the study of nature as a sure path toward the revelation of divine wisdom, who began their academic careers as professors of mathematics. Both valued the learning of the ancients, searching ever further into the pagan and Christian past in hope of illumination. For significant portions of their respective careers, that knowledge was found in the occult sciences. In all these respects, they typified the Christian encyclopedic approach to nature that humanists had practiced since the fifteenth century. They were quite probably, along with Leibniz, the last great humanist natural philosophers of the early modern period.

Despite these many similarities we do not usually place the German Jesuit Athanasius Kircher (1602–80) and the English philosopher Isaac Newton (1642–1727) side by side. For almost two centuries, they have inhabited the separate worlds created by modern histories of science and, to a lesser degree, articulated by intellectuals at the end of the seventeenth century who had begun to make these distinctions themselves.